Popular smoking articles, such as cigarettes, have a substantially cylindrical rod-shaped structure and include a charge, roll or column of smokable material, such as shredded tobacco (e.g., in cut filler form), surrounded by a paper wrapper, thereby forming a so-called “smokable rod” or “tobacco rod.” Normally, a cigarette has a cylindrical filter element aligned in an end-to-end relationship with the tobacco rod. Typically, a filter element comprises plasticized cellulose acetate tow circumscribed by a paper material known as “plug wrap.” A cigarette may incorporate a filter element having multiple segments, and one of those segments may comprise activated charcoal particles. See, for example, U.S. Pat. No. 6,537,186 to Veluz; U.S. Pat. App. Pub. No. 2007/0056600 to Coleman III, et al.; and PCT Pub. No. WO 2006/064371 to Banerjea; each of which is incorporated herein by reference. Typically, the filter element is attached to one end of the tobacco rod using a circumscribing wrapping material known as “tipping paper.” It also has become desirable to perforate the tipping material and plug wrap to provide dilution of drawn mainstream smoke with ambient air. Descriptions of cigarettes and the various components thereof are set forth in Tobacco Production, Chemistry and Technology, Davis et al. (Eds.) (1999) and U.S. Pat. No. 7,503,330 to Borschke et al, which is incorporated herein by reference.
A cigarette is employed by a smoker by lighting one end thereof and burning the tobacco rod. The smoker then receives mainstream smoke into his/her mouth by drawing on the opposite end (e.g., the filter end) of the cigarette, until the tobacco rod is partially or completely consumed, after which the remaining cigarette portion is discarded.
The discarded portion of the cigarette rod typically is primarily composed of the filter element, although it may include most or all of a tobacco rod. In general, cigarette filters include solvent cross linked cellulose acetate fiber bundles wrapped in two layers of paper. The first layer of paper, often referred to as plug wrap, holds the fiber bundle together in a rod form and may include a glue line to anchor the fiber bundle to the plug wrap paper; the second layer, often referred to as the tipping, is fully adhered to the plug wrap and attaches the filter tube to the wrapping material surrounding the cigarette's tobacco rod. Cigarette filters may be slow to degrade or disperse in some environments. This is generally attributed to the tightly bound nature of the filter plug's design which is configured to provide a specified filtering effect, but which may insulate the majority of the filter from certain environmental effects upon disposal.
The most commonly used polymer in cigarette filter manufacture is cellulose acetate that has a degree of acetate substitution of about 2.5 acetate groups per anhydroglucose unit group. During manufacture, the acetate polymer typically is extruded as a fiber tow, and mixed with one or more plasticizers (e.g., triacetin, polyethylene glycol, glycerin). Cellulose acetate tow processes are set forth, for example, in U.S. Pat. No. 2,953,838 to Crawford et al. and U.S. Pat. No. 2,794,239 to Crawford et al., which are incorporated herein by reference. Various fluids may be injected and distributed to the multifilament fiber tow used in the manufacture of tobacco smoke filters. These fluids, which may be injected and distributed into the tow alone or in combination with liquid or gaseous carriers, may be flavorants, tow blooming agents, lubricants, sizing solutions, finish compositions, plasticizers, or the like. Such fluids are intended to impart desired physical or flavor characteristics to the fluid-treated tow. Fluid injection processes are set forth, for example, in U.S. Pat. No. 5,387,285 to Rivers, which is incorporated herein by reference.
The cellulose acetate fibers that form the filter element typically are coated with a fiber finish composition. Such compositions are generally water based emulsions comprising multiple components. Each component may serve a specific function either during processing of the fibers or during subsequent use of a filter formed from the fibers. Typical components of a fiber finish composition include lubricating oils to reduce friction so that the fibers can be processed without breakage, anti-static agents to reduce static build-up on the fibers, and emulsifiers to inhibit phase separation in a fiber formulation during processing. Other auxiliary components may include anti-microbial agents, hydrophilic agents, or other reactive compounds. After assembly of fibrous tow into filter-ready material, plasticizers may be applied to soften the fiber and to enable inter-fiber bonds to form to harden the filter to a desired hardness/consistency. The surface chemistry of cellulose acetate and plasticizer may provide for a smoke flavor that is widely desired and accepted by smokers. This may be due in part to the well-known ability of cellulose acetate and plasticizer to reduce naturally occurring phenolic compounds from tobacco smoke. Certain other filter designs/formulations may provide a different smoke flavor. To date, non-cellulose acetate tow filters have not generally been accepted nor met with commercial success.
It would be highly desirable to provide a smoker with an enhanced smoking experience, such as can be accomplished by providing a filtered cigarette including a filter element having particular design features. To that end, it would be desirable to provide a filter element for a cigarette that is capable of selectively filtering various components of the mainstream smoke produced during use of the cigarette. It may be desirable to formulate the fiber finish composition employed in a particular filter segment to provide a desired surface chemistry for selective vapor phase compound removal. It may be desirable to provide a filter element including multiple filter segments, each having a surface chemistry formulated to selectively interact with specific vapor phase compounds.